As one kind of semiconductor devices, a NAND type flash memory device having a three-dimensional structure is known in the art. In the manufacture of the NAND type flash memory device having the three-dimensional structure, by performing an etching process of etching a multilayered film in which silicon oxide films and silicon nitride films are alternately stacked on top of each other, a deep hole is formed in the multilayered film. This etching process is described in Patent Document 1.
To be specific, in Patent Document 1, there is disclosed a method of etching a multilayered film by exposing a processing target object having a mask on the multilayered film to plasma of a processing gas.
Patent Document 1: US Patent Application Publication No. 2013/0059450
A processing target object to be etched may include a first region including a multilayered film in which silicon oxide films and silicon nitride films are alternately stacked on top of each other; and a second region including a single-layered silicon oxide film. It is required to form spaces such as a hole and/or a trench in both of the first region and the second region by etching the processing target object. Further, when performing this etching process, it is also required that a depth of the space formed in the first region and a depth of the space formed in the second region be substantially same, a deformation degree of a planar shape of the space be small, and, especially, the deformation degree of the space at a bottom portion (deep portion) thereof be small. Here, the deformation of the space refers to a phenomenon that an actually formed space has a planar shape different from a required planar shape. For example, if the required planar shape is a circular shape, the deformation of space refers to a phenomenon that the actually formed space has a planar shape different from the circular shape.